This is a macOS10.13 issue, specific for some Intel GPU cards. Apple has fixed(partially) this issue inside macOS10.13.4 released build.
Following are the workaround for resolving this issue.
1) Update your mac machine to latest macOS10.13.4. Here, Apple has fixed this issue to some extent. You will face very less number of rendering issues.
2) Disable GPU preview and set display performance as typical.
Once you have updated to macOS10.13.4 .You might still face some rendering issues. Since, Apple has not fixed this issue completely.
Please switch off GPU rendering for these cases and report a separate post for tracking.Anonymous commented
I am having the same issue with my new iMac 2018 (high Sierra), 27-inch, Radeon Pro 570 4096 MB graphics -running 10.13.4
In all three Adobe CS6 programs, Illustrator, Photoshop and InDesign - I'm having display issues with pixilated type, menus etc. Like others in this forum, the sole reason for buying this mac is for design, which is a daily frustration now.
1) Others mentioned "switch off GPU rendering" - I cannot locate this - is this only an option in CC"?
2) Is there a FIX for these Adobe pixelation issues that can be addressed for CS6 on my new iMac?
Please HELP / please advise..